1. Field of the Invention
The present invention relates to an electromagnetic fuel injection valve and a method of manufacturing the same, both of which are mainly used for a fuel supply system of an internal combustion engine.
2. Description of the Related Art
The configuration of this kind of a general fuel injection valve will be described in accordance with FIG. 5. As shown in FIG. 5, a fuel injection valve 1 has a solenoid device 2 disposed inside a resin molding portion 10, a core 3, and a housing 14 which constitutes a magnetic path, those of which are integrally formed.
Furthermore, a rod which adjusts a load of a spring 9 is fixed inside the core 3, and the core 3 and a holder 15 are fixed by welding to the housing 14 which constitutes the magnetic path.
Further, a movable valve element 7, a plate 11 having an injection hole part 11a, and a valve seat unit 8 which is mounted to or removed from the valve element 7 to form a valve mechanism are provided inside the holder 15; and the valve element 7 is composed of an armature 4, a valve section 6, and a pipe section 5 which joins the armature 4 and the valve section 6 at both ends of the pipe section 5. The armature 4 and the valve section 6 of the valve element 7 uses high hardness metal in consideration of abrasion durability and the whole of the valve element 7 is integrally manufactured by cutting.
Under such a configuration, usually, the valve element 7 is pressed to a valve seat 8a side of the valve seat unit 8 by a spring 9 and accordingly the fuel injection valve 1 is in a closed valve state. When the solenoid device 2 is energized, the armature 4 is suctioned to the core 3 side by a magnetic sucking force generated in the solenoid device 2 and the valve element 7 moves to the core 3 side; and accordingly, a gap is generated between the valve section 6 and the valve seat 8a of the valve seat unit 8 and the valve element 7 is in an opened valve state. As a result, fuel flows through the gap and the injection hole part 11a. 
In such conventional fuel injection valve 1, the armature 4 and the valve section 6 of the valve element 7 are joined by welding or the like; and therefore, the pipe section 5 is made of metal. As a result, a mass of the valve element increases and when the valve is opened or closed, the armature 4 hits the core 3 and the valve section 6 hits the valve seat 8a; and accordingly, a noise is generated between the armature 4 and the core 3 and between the valve section 6 and the valve seat 8a. 
As a technique of reducing such noise, one in which emission to the outside of a collision sound is reduced has been devised, for example, a soundproof effect is improved by improving the rigidity of peripheral components of the valve element 7 and the resin molding portion 10 is formed in a double-layered structure consisting of different materials (Patent Documents 1 and 2)
However, such technique has problems of a cost increase due to an increase in the number of components and man-hours and an increase in weight of the fuel injection valve 1.
Furthermore, a technique of absorbing collision energy and reducing the collision sound by placing a vibration proofing member on the periphery of the valve seat 8a, has been devised (Patent Document 3). Also this case has a problem of a cost increase due to an increase in the number of components and degradation in assembly property.
Further, in recent years, due to an improvement in spray targeting property, the distance from the mounting section 1a of the fuel injection valve 1 to the injection hole part 11a tends to increase so as to deeply enter the injection hole part 11a of the fuel injection valve 1 into the inside of an intake pipe or a cylinder head of an internal combustion engine. Therefore, a problem exists in that the pipe section 5 of the valve element 7 is long; and accordingly, the mass of the valve element 7 increases and the collision sound further increases.